I'll throw in a few things to answer your ? - all based on my opinion, then another opinion on how distro works versus how assists are doled out:
1 - the best way to have a player with high assists per game - say leading the nation is have 5 things -
a - extrememly low distro (more fg's made by everyone else, more chances for your guy to assist)
b - high passing in the player in ?, playing PG not SG
c - bad passing for the rest of his team (the most important factor in getting assists IMO after high passing in the player)
d - speed in the passer
e - good offensive team mates
bonus - if you are trying for high assists per game, rather than high assists per minute, you need stamina and no full court press so the guy is on the court around 30 minutes plus
2 - assists are calculated after the shot is made, the assist factor for each non scoring player is calculated as odds, and as I said is highly PAssing dependant, hence distro does not affect assists directly, although as in point 1a, a high distro player has fewer chances for assists, because he can't assist on his own makes - generally speaking (say 80%), distro will track how many shot attempts, ft attempts, and turnovers a player makes - the remaining shots are more as result of fastbreak steals and offensive rebounds, and are less dependant on the distro settings.